1. RM-MAC: A Routing-Enhanced Multi-Channel MAC Protocol in Duty-Cycle Sensor Networks Ye Liu, Hao Liu, Qing Yang, and Shaoen Wu In Proceedings of the IEEE ICC, London, UK, June 2015 Nov. 10, 2015 Minwoo Joo (mwjoo@korea.ac.kr)

2. Outline Introduction Related Work RM-MAC Protocol Design Performance Evaluation Conclusion 2

3. Introduction Multi-channel MAC Protocols in WSNs Recently, multi-channel MAC protocols have attracted considerable interests from the research community since current WSN hardware (e.g., MICAz and TelosB) already support multiple channels communication Advantages Efficient support for multi-task Reliable and timely communication Collision reduction 3 [2] P. Huang, L. Xiao, S. Soltani, M. Mutka, and N. Xi, "The evolution of mac protocols in wireless sensor networks: A survey," IEEE Communications Surveys Tutorials, vol. 15, no. 1, pp. 101-120, First Quarter 2013.

4. Introduction Existing Multi-channel MAC Protocols They obtain better communication performance than single channel MAC protocols by mitigating interference from other nodes However, their multi-hop data forwarding is not fast enough to support delay-sensitive applications The duty cycling operation poses challenge on sleep delay for multi-hop data forwarding Multiple channels access approaches are weak for supporting multi-hop broadcast due to frequency diversity of neighbors 4

5. Introduction RM-MAC: Routing-enhanced Multi-channel MAC It assigns channel polling time based on cross-layer routing information Advantages Multi-channel MAC protocol Low delivery latency Multi-hop broadcast support in an energy efficient fashion 5

6. Related Work 6

7. RM-MAC Protocol Design System Model Each node is equipped with a single half-duplex radio to transmit or receive packet Each time slot is further split into multiple subslots, which is long enough for a round-trip packet transmission frame → slot → subslot Sensor nodes in the network operate at a duty-cycle model i.e., active state and dormant (i.e., sleep) state Each node picks one of subslot in every slot to poll channel for possible traffic (remaining subslots for the dormant state) A node can receive a packet only in its channel polling time unit A node wake up to transmit packet according to working schedule of the intended receiver 7

8. RM-MAC Protocol Design Frequency Selection in each Time Slot (same as MuCHMAC) RM-MAC adopts hybrid design (FDMA+TDMA) to avoid interference Pseudo-random channel-switching scheme is used so that a sender can accurately predict the listening channel of a receiver as well as reduce memory overhead The pseudo-random function to generate channel hopping sequence for a node is given as follows 8

9. RM-MAC Protocol Design 9 BCD BCD BCD BCD BCD BCD BCD BCD BCD BCD ABCD

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11. RM-MAC Protocol Design Channel Polling Subslot Assignment in RM-MAC It exploits a cross-layer design to mitigate sleep latency introduced by duty cycling as well as maximizing parallel transmissions Every node calculates channel polling subslot assignment based on its hop distance to the sink node 11 Sink wait for next time slot within one time slot

12. RM-MAC Protocol Design 12

13. RM-MAC Protocol Design Ripple Broadcast Mechanism in RM-MAC The ripple broadcast mechanism can accelerate multi-hop forwarding of broadcast and mitigate the broadcast storm issue Each node selects broadcast period according to its hop distance to the sink Advantages Short interval between consecutive broadcasts Reduced redundant reception and medium contention 13

14. Performance Evaluation ns-2 based Simulations 14

15. Performance Evaluation 15

16. Performance Evaluation 16

17. Performance Evaluation 17

18. Conclusion This paper presented the design and evaluation of RM-MAC, a multi-channel MAC protocol for duty-cycle sensor networks Channel polling subslot based on hop distance Ripple broadcast mechanism We conducted a comprehensive evaluation through ns-2 which shows that RM-MAC significantly outperformed MuCHMAC 18

19. Thank You. Q & A 19